Name: _____________________________________________________
Hour: ________
Atomic Timeline Project
Chemistry A
Purpose:
To help you piece together the story of what we know about the "atom", you will be creating a
timeline depicting the development of the scientific model of the atom. It has been through new
discoveries by philosophers and scientists in chemistry, as well as physics, that the model of the
atom has expanded and changed over time. Your assignment is to research the major
contributors and significant discoveries that have impacted the atomic model and, from this
material, develop a timeline.
Requirements:
Your timeline MUST:
1. Match each of the 11 scientists and/or philosophers located below to key dates, their
contributions to the atomic model and a visual representation of their contribution.
2. Be chronological in its sequence, with the dates clearly shown (it need not be to scale), and at
a minimum include the information contained below.
3. Be neat and legible.
4. Be larger than 8.5 x 11 inch size but no larger than half of a posterboard. This could involve 2
sheets (or more) of typing paper posted on cardboard, for example. I highly recommend posting
any type of typing paper on cardboard for support!
Deadlines and Guidelines:
• Your timeline is due on ____________________. All procedures for late work are to be
followed for this project.
• You are welcome to work (but NOT copy) together in gathering your information, but your
timelines are to be completed independently of one another!
• You do not have to follow the typical horizontal timeline format; you may be creative and use
any format you wish.
Extra Credit:
• Extra credit may be given for the inclusion of other atomic scientists and/or philosophers as
well as for creativity. Additional scientists that may be included are Wilhelm Roentgen (1895),
Henri Becquerel (1896) and Marie & Pierre Curie (1898)
 All required information for the original group of atomic scientists and/or philosophers should
be included. A maximum of 5 additional scientists may be included for extra credit. Extra
credit points will be awarded at my discretion and will be based on content.
Recommended Sources:
Your textbook is probably the best source of information for this project. Often the descriptions
are easier to understand that what you might find on a website. Also, dates may vary on
different websites.
If you choose to use a website, I would find one that is not WAAY more complicated than you
need. Try searching “atomic timeline” from a search engine like Google.
Part 1: Scientists/Philosophers with Dates
Henry Moseley (1914)
John Dalton (1803)
Dimitri Mendeleev (1869)
JJ Thomson (1898)
Robert Millikan (1909)
Democritus (460-370 BC)
James Chadwick (1932)
Niels Bohr (1922)
Ernest Rutherford (1911)
Erwin Schroedinger (1926)
Werner Heisenberg (1927)
Part 2: Descriptions of Contributions
Developed the Quantum Mechanical Model of the atom, which treats electrons like waves.
Improved upon the Bohr Diagram of the atom with his Electron Cloud Model.
Identified the neutron, the final subatomic particle. He concluded that the nucleus is made of
both protons and neutrons.
Developed modern atomic theory: matter is composed of atoms, atoms are identical in size,
mass etc, atoms cannot be created, divided or destroyed, atoms combine into compounds
and in chemical reactions atoms are separated, combined or rearranged.
Proposed the nuclear atomic model with a centrally located, positively charged nucleus
based on the result of his Gold Foil Experiment.
Discovered that atoms of each element contain a unique number of protons, referred to as
the element’s atomic number. Reorganized the periodic table to create what we use today.
First person to propose that matter was not infinitely divisible. First person to use the latin
term “atomos”, which means “atom”.
Developed the Heisenberg Uncertainty Principle, which states that the exact position or
location of an electron in an atom cannot be predicted.
Identified the electron (first subatomic particle) using cathode ray tubes. Proposed the plum
pudding (chocolate chip cookie) model of the atom.
Determined the charge and mass of an electron using the Oil Drop Experiment.
Proposed that the lowest allowable energy state of an atom is called its ground state and
when an atom gains energy it is said to be in an excited state. Suggested that electrons move
around the nucleus in shells, which relate to the energy level of the electron.
Organized the elements into the first periodic table, which was based on the mass of each
element.
Part 3: Visual Representations of Contributions
----------------------------------------------------------------Name: _____________________________________
Hour: ________
Atomic Timeline Grading Rubric
Date in Order
Correct
Description
Correct
Diagram
Neat/Legible
Heisenberg
Mendeleev
Thomson
Rutherford
Millikan
Dalton
Chadwick
Bohr
Schrodinger
Democritus
Moseley
** Cut this half of the paper off and attach to your timeline when you turn it in**
Points:
/11
/22
/11
/6
Extra Credit
Total:
/50